The structural and functional properties of folded chromosomes in the yeast, Saccharomyces cerevisiae, will be studied in relation to two differentiative processes--the cell cycle and the meiotic phase of the life cycle. These studies will include a sedimentation analysis of folded chromosomes isolated from cells at various stages of the cell cycle and from various meiotic stages. An essential component of these studies will be an analysis of folded chromosomes isolated from mutants which arrest at specific stages in the cell cycle or meiosis. In addition, a gel electrophoresis of the proteins from the folded chromosomes from both wild-type and mutant cells will be carried out in order to examine their role in tertiary chromosome structure and function. DNA-dependent ATPase and topoisomerase activities and their relationship to folded chromosomes will also be characterized.